Preheat oven to 350 degrees. Line three baking sheets with parchment paper or silpat liners.
In mixer cream together sugar, shortening, vanilla and egg. In a small bowl sift together dry ingredients. Add to creamed sugar, 3/4 cup at a time, alternating with the buttermilk. When combined stir in morsels.
Drop by tablespoonfuls (I use a tablespoon scoop) onto lined baking sheets and bake 8 minutes. Remove from oven and add a marshmallow half to each cookie, return to oven and cook 3 minutes longer. Let cookies cool 1 minute on sheet then remove to racks to cool completely. Using a measured tablespoon scoop this recipe makes 3 dozen cookies.